Chinese Defense Minister Chang Wanquan has warned of maritime security threats and called for increased preparations for what he termed a “people’s war at sea” as Beijing seeks to “safeguard sovereignty” after last month’s international tribunal ruling rejected its historic claims to much of the South China Sea.

Chang, who was speaking during an inspection in coastal Zhejiang province, “called for recognition of the seriousness of the national security situation, especially the threat from the sea,” the official Xinhua News Agency reported Tuesday.

The military, police and public should prepare for mobilization to defend national sovereignty and territorial integrity, he was also quoted as saying.

Chang’s comments come at a time of heightened tensions in the South China Sea after a tribunal with the Permanent Court of Arbitration (PCA) at The Hague ruled against Beijing’s claims to virtually the entire strategic waterway, through which more than $5 trillion in annual trade passes.

China rejected the decision, blasting the proceedings as a “farce” and calling the ruling “waste paper.”

China has stoked regional concerns after it constructed man-made islands on some of the features it controls in the South China Sea, building military-grade infrastructure, including airstrips and radar facilities on some of the islets.

Beijing announced last week that it would hold joint naval drills in the waters with Russia in September. China’s Defense Ministry called the drills “routine,” saying they were not directed at any third party.

Also Tuesday, China’s Supreme Court said people caught illegally fishing in Chinese waters could be jailed for up to a year, issuing a judicial interpretation defining those waters as including the country’s exclusive economic zones.

The court said none of China’s reefs and holdings in the South China Sea’s Spratly chain entitled it to a 200 nautical mile (370-km) EEZ.

The court made no direct mention of the South China Sea or the tribunal ruling, but said its judicial interpretation was made in accordance with both Chinese law and the United Nations Convention on the Law of the Sea (UNCLOS), under which the Philippines had brought the case to the PCA.

“Judicial power is an important component of national sovereignty,” the court said in a statement, adding, “People’s courts will actively exercise jurisdiction over China’s territorial waters, support administrative departments to legally perform maritime management duties, equally protect the legal rights of Chinese and foreign parties involved and safeguard Chinese territorial sovereignty and maritime interests.”